Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$184.81	8.683%	$200.8571	$200.86	$200.85	$200.90
Purchase #2	$237.40	8.193%	$256.8502	$256.85	$256.85	$256.90
Purchase #3	$183.52	8.492%	$199.1045	$199.10	$199.10	$199.10
Purchase #4	$66.36	7.456%	$71.3078	$71.31	$71.30	$71.30
Purchase #5	$248.71	4.609%	$260.173	$260.17	$260.15	$260.20
Purchase #6	$188.56	6.365%	$200.5618	$200.56	$200.55	$200.60
Purchase #7	$48.90	8.422%	$53.0184	$53.02	$53.00	$53.00
7 purchase totals =	$1,158.26		$1,241.8728	$1,241.87	$1,241.80	$1,242.00